Hive's DML data manipulation

data import

1. Load data into the table (Load)
   usage:
   
   

   hive>load data [local] inpath '/opt/module/datas/student.txt' [overwrite] into table student [partition (partcol1=val1,…)]; (1) load data: means to load data (2) local : Indicates loading data from local to hive table; otherwise, loading data from HDFS to hive table (3) inpath: Indicates the path to load data (4) into table: Indicates which table to load into (5) student: Indicates a specific table ( 6) overwrite: means overwriting the existing data in the table, otherwise means appending (7) partition: means uploading to the specified partition

   Practical case:
   
   

   create a table	hive (default)> create table student(id string, name string) row format delimited fields terminated by '\t';
   Load local files to hive	hive (default)> load data local inpath '/opt/module/datas/student.txt' into table default.student;
   Load HDFS file into hive	Upload files to HDFS hive (default)> dfs -put /opt/module/datas/student.txt /user/lzl/hive; load data on HDFS hive (default)>load data inpath '/user/lzl/hive/student .txt' into table default.student;
   Loading data overwrites existing data in the table	Upload files to HDFS hive (default)> dfs -put /opt/module/datas/student.txt /user/lzl/hive; load data to cover the existing data in the table hive (default)>load data inpath '/user/ lzl/hive/student.txt' overwrite into table default.student;

2. Insert data into a table through a query statement (Insert)
   
   

   Create a partition table	hive (default)> create table student(id string, name string) partitioned by (month string) row format delimited fields terminated by '\t';
   basic insert data	hive (default)> insert into table  student partition(month='201805') values('1004','wangwu');
   Basic schema insertion (query results based on a single table)	hive (default)> insert overwrite table student partition(month='201805')                         select id, name from student where month='201806';
   多插入模式（根据多张表查询结果）	hive (default)> from student               insert overwrite table student partition(month='201805')               select id, name where month='201809'               insert overwrite table student partition(month='201806')               select id, name where month='201809';

3. 查询语句中创建表并加载数据（As Select）
   详情查看https://blog.csdn.net/liangzelei/article/details/80147866中的创建表
   根据查询结果创建表（查询的结果会添加到新创建的表中）
   create table if not exists student3
   as select id, name from student;
   
4. 创建表时通过Location指定加载数据路径
   
   

   创建表，并指定在hdfs上的位置	hive (default)> create table if not exists student5(id int, name string)                         row format delimited fields terminated by '\t'                         location '/user/hive/warehouse/student5';
   上传数据到hdfs上	hive (default)> dfs -put /opt/module/datas/student.txt  /user/hive/warehouse/student5;
   查询数据	hive (default)> select * from student5;

5. Import数据到指定Hive表中
   
   

   先用export导出后，再将数据导入 （注意支持出export导出的文件）

   hive (default)> import table student2 partition(month='201709') from '/user/hive/warehouse/export/student';

数据导出

1. Insert导出
   
   

   将查询的结果导出到本地	hive (default)> insert overwrite local directory '/opt/module/datas/export/student'                         select * from student;
   将查询的结果格式化导出到本地	hive (default)> insert overwrite local directory '/opt/module/datas/export/student1'                ROW FORMAT DELIMITED FIELDS TERMINATED BY '\t' COLLECTION ITEMS                TERMINATED BY '\n'                select * from student;
   将查询的结果导出到HDFS上(没有local)	hive (default)> insert overwrite directory '/user/atguigu/hive/warehouse/student2'             ROW FORMAT DELIMITED FIELDS TERMINATED BY '\t' COLLECTION ITEMS             TERMINATED BY '\n'              select * from student;

2. Hadoop命令导出到本地
   
   

   hive (default)> dfs -get /user/hive/warehouse/student/month=201805/000000_0  /opt/module/datas/export/student3.txt;

3. Hive Shell 命令导出
   
   

   $ bin/hive -e 'select * from default.student;' > /opt/module/datas/export/student4.txt;

4. Export导出到HDFS上
   
   

   hive (default)> export table default.student to '/user/hive/warehouse/export/student';

5. Sqoop导出
   未完待续......

清除表中数据

hive (default)> truncate table student;

注意：Truncate只能删除管理表，不能删除外部表中数据